The nail is formed by corneocytes that are flattened in a plane and stacked one on top of the other in a "brick-wall" arrangement. Keratin fibrils found within the corneocytes provide strength and flexibility to the cells due to the presence of cystine disulphide bridges, which are found at a level of about 9.4% by weight in the nail. In addition, the intercellular adhesive factors which hold corneocytes together also provide strength and flexibility. These intercellular adhesive factors are: (1) intercellular cement, which contains lipids (2) desmosomes, and (3) gap junctions and narrow junctions.
Brittle, unhealthy nails usually result from some disruption in the normal levels of intercellular adhesive factors. This can occur through nail dehydration, infections, exposure to toxic agents, injuries, and so on.
Compositions for application to nails to effect strengthening are well known in the art. However, since the biology of the nail is not well understood, it has been difficult to formulate compositions which contain ingredients which are capable of interacting with the nail plate to provide a beneficial result. One other problem with current nail strengthening agents is that the user cannot usually apply nail polish on top of the strengthening agent Obviously this poses a disadvantage, since women who are interested in strengthening nails tend to be the same women who wear nail enamel.
There is a need in the art for nail strengthening compositions which contain ingredients which are capable of reacting with the nail itself to provide enhanced results and which are capable of use with or without nail enamel.